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Avalanche Forecast

Archived

Dec 30th, 2018–Dec 31st, 2018

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

Sea To Sky.

The forecast calls for a stable weather pattern in the next few days.

Confidence

High -

Weather Forecast

MONDAY: Mix of sun and cloud / Light north wind / Alpine temperature -3 CTUESDAY: Mix of sun and cloud / Light northwest wind / Alpine temperature -3 CWEDNESDAY: Flurries / Moderate southwest wind / Alpine temperature 0 C / Freezing level 1500 m

Avalanche Summary

Avalanche activity on Sunday was reported as a few explosives controlled size 1-1.5 storm and windslabs. On Saturday reports indicated several explosives controlled size 2 storm and wind slabs in the alpine and tree line. Some of these avalanches were running on a layer of surface hoar buried around December 26. There was also a report of a size 3 storm slab avalanche that released sympathetically to an avalanche that was set of by an explosive about 30m away.

Snowpack Summary

30-50 cm of recent new snow from the past 7 days potentially sits on a weak layer of feathery surface hoar in the tree line elevation band. Snow amounts will be deepest and touchiest in the lee of terrain features immediately adjacent to ridges.Below 1800 m, around 50 cm of storm snow may not be bonding well to an underlying crust (see here).A weak layer of sugary facets and surface hoar lies around 150 to 200 cm deep in the snowpack. There hasn't been reports of avalanches on this layer for over a week. That being said, this layer may still exist in isolated areas around treeline in some portions of the region.At the base of the snowpack, weak and sugary facets are found below an early-season melt-freeze crust. This weak layer has been the culprit for sporadic, very large avalanches in alpine terrain in the past few weeks. The avalanches have occurred in areas where the ground roughness is very smooth, for example glaciers, firn, and shale/rock slab slopes. An avalanche could be triggered in this layer with a very large trigger, such as a cornice fall.

Problems

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.